1. The Field of the Invention
The present invention relates to an aerodynamic drag reduction system for use on trucks and trailers. More specifically, the invention relates to a drag reducing, aerodynamic fairing that can be quickly and temporarily attached to the rear of a trailer to reduce aerodynamic drag.
2. Background and Relevant Technology
The design of a moving vehicle has always been viewed, at least in part, as both cosmetic and utilitarian. Cosmetic-based design features are based primarily on enhancing the appeal of a vehicle to the consuming public. Utilitarian-based features, on the other hand, are based on what the vehicle must have to be effective for its intended purpose. For example, the engine and vehicle size are determined, in part, by how many passengers the vehicle should carry, or what size load must be transported.
In recent years, utilitarian and cosmetic concerns have merged to increase focus on preserving cosmetic appeal, while also making the vehicles more efficient so as to reduce fuel costs. As a result, the designs of many moving vehicles have undergone significant changes, in both shape and design, so as to make the vehicles more aerodynamic.
In the United States trucking industry, an estimated 1.7 million tractors carry an estimated 4.5 million commercial trailers and consume approximately 23 billion gallons of diesel fuel each year. When traveling at highway speeds, approximately 65–70% of the energy generated from the fuel is used solely to overcome aerodynamic drag on the tractor and trailer. Many aerodynamic improvements have been made to the front sides of trailers and tractors to combat costly aerodynamic drag. The addition of streamlined fairings and other aerodynamic features has, over the past two decades, helped to increase the fuel economy of a tractor and trailer from about 4.5 miles per gallon to approximately 6 miles per gallon.
While these aerodynamic design improvements at the front of the tractor and trailer have resulted in some improvement to fuel economy, aerodynamic drag continues to be a costly problem. This problem continues, in part, because of the design of the back end of the trailer. The design of the back end of the trailer has not improved significantly over the past twenty-five years, and the back end of most trailers is still squared-off. This squared-off, back end hinders aerodynamic flow around the trailer, and still creates significant drag on the vehicle which results in the consumption of large amounts of fuel.
As with any vehicle, when the trailer body moves through the air, a mass of air is displaced and must flow around the vehicle. As the air flows toward the squared-off, back end of a semi-tractor trailer, areas of low-pressure are created. These areas cause sudden, high-energy, chaotic inrushings of turbulent air which creates drag. An aerodynamic shape extending out from the rear of a semi-tractor trailer helps control, slow, and shape the flow of inrushing air, thus decreasing the drag forces.
While many solutions to improve the aerodynamic drag at the rear of the semi-tractor trailer have been suggested, none have been widely adopted by truckers or trailer companies. Various reasons exist for this. First, semi-tractor trailers are not generally designed for aerodynamic efficiency. The trailers are designed to maximize interior space for carrying cargo, and the external dimensions of the trailer are set by state and federal highway limitations. Second, semi-tractor trailers are often loaded and unloaded at a loading dock. In order to use a loading dock, it is necessary to back the trailer up so that it is flush against the dock. This requires the trailer's back end to be planar. Therefore, any aerodynamic device secured to the distal end of a semi-tractor trailer must be easily removable or repositionable to accommodate loading and unloading at a dock. Further, the person with the highest degree of interest in aerodynamic improvements to semi-tractor trailers is the one paying for the fuel required to pull the trailer. In many cases, the owner of the trailer is not the person paying for the fuel. As a result, the owner has little interest in ensuring that the trailer is aerodynamically designed for improved fuel efficiency.